1. Field of the Invention
The present invention relates to an actuator apparatus utilizing a shape-memory alloy.
2. Description of the Related Art
In recent years, actuators using shape-memory alloys have been provided. An example of these actuators is a cable having a bending mechanism disclosed in Japanese Utility Model Disclosure (Kokai) No. 61-94001. In this apparatus, a plurality of actuators having shape-memory alloys are placed in a cable, and the actuators are independently energized to bend the cable.
That is, power supply lines are independently connected to the actuators including a shape-memory alloy, and an actuator to be activated is energized via the independent power supply line or the supplied power is changed for each actuator, thereby controlling operations of the actuators.
In this conventional actuator apparatus, however, the independent power supply line is connected to each shape-memory alloy constituting the actuator. Therefore, the number of power supply lines is increased in proportion to the number of actuators or shape-memory alloys. That is, since each shape-memory alloy requires two power supply lines, the total number of power supply lines required becomes twice that of shape-memory alloys.
Since an electrical resistance of a shape-memory alloy is generally low, a higher current value is required for heating the shape-memory alloy. For this reason, a power supply line must have a relatively high current capacity. Therefore, a large-diameter wire material is used for a power supply line.
Wiring using a large number of electrical wires having a large diameter is very problematic in realizing a compact and light actuator. In addition, a large-diameter electrical wire is undesirable if an actuator is applied to a cable apparatus or an endoscope which is long in shape because the length of a power supply line is also increased. Also, when a power supply time is prolonged or power supply is repeatedly performed, heat generated from power supply lines may be accumulated to lead to overheating.